material-components_material-components-ios/components/BottomNavigation

Bottom navigation

Bottom navigation bars allow movement between primary destinations in an app. Tapping on a bottom navigation icon takes you directly to the associated view or refreshes the currently active view.

Contents

• Using bottom navigation
• Bottom navigation bar
• Theming

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Using bottom navigation

Installing

In order to install bottom navigation with Cocoapods first add it to your Podfile:

pod 'MaterialComponents/BottomNavigation'

Then, run the following command:

pod install

From there, import the relevant target or file and instantiate your view.

Swift

import MaterialComponents.MaterialBottomNavigation

Objective-C

#import "MaterialBottomNavigation.h"

Bottom navigation classes

MDCBottomNavigationBar is the iOS bottom navigation implementation. MDCBottomNavigationBar can be added to a view hierarchy like any UIView. Material Design recommends always placing bottom navigation components at the bottom of the screen.

MDCBottomNavigationBar works much like a UITabBar and both are populated with an array of UITabBarItem instances. However, MDCBottomNavigationBar is built with Material Design in mind and should be used with other Material Design components where possible to provide a consistent look and feel in an app. Additionally, while MDCBottomNavigationBar has similar features to MDCTabBar, MDCTabBar is chiefly intended for top navigation, whereas MDCBottomNavigationBar--as the name indicates--is intended for bottom navigation.

It is recommended that a bottom navigation bar contain anywhere from three to five items. If there are fewer than three destinations, consider using Material tabs instead. If your top-level navigation has more than six destinations, provide access to destinations not covered in bottom navigation through alternative locations, such as a navigation drawer.

Title visibility in MDCBottomNavigationBar can be configured in three ways:

1. To only show the title of the selected item.
2. To always show title regardless of any item's selection state
3. To never show title regardless of any item's selection state.

The default behavior of MDCBottomNavigationBar is to only show the title for an item that is selected.

In landscape orientation, items can be configured to be justified or compactly clustered together. When items are justified the bottom navigation bar is fitted to the width of the device. Justified items can have their titles shown below their respective icons or adjacent to their respective icons.

Making bottom navigation accessible

To help ensure your bottom navigation item is accessible to as many users as possible, please be sure to review the following recommendations:

• Ensure that your UITabBarItem instances have their accessibilityLabel properties set. Setting a new accessibilityLabel on a UITabBarItem will result in the corresponding bottom navigation bar item's accessibilityLabel changing.

• Set an appropriate accessibilityValue value if your item has a badge value. For example, an item with an inbox icon with a badge value for how many emails are unread. You should explicitly set the accessibilityValue when the badge value doesn't provide enough context. For example, in an inbox example simply having the value "10" doesn't provide enough context, instead the accessibility value should explain what the badge value symbolizes. The default value if there is a badge value and you haven't set any accessibilityValue will be that the accessibilityValue is the badgeValue.

Swift

tabBarItem.accessibilityValue = "10 unread emails"

Objective-C

tabBarItem.accessibilityValue = @"10 unread emails";

Minimum touch size

Make sure that your bottom navigation bar respects the minimum touch area. The Material spec calls for touch areas that should be least 48 points high and 48 wide.

Swift

override func viewWillLayoutSubviews() {
  super.viewWillLayoutSubviews()
  let size = bottomNavBar.sizeThatFits(view.bounds.size)
  let bottomNavBarFrame = CGRect(x: 0,
    y: view.bounds.height - size.height,
    width: size.width,
    height: size.height
  )
  bottomNavBar.frame = bottomNavBarFrame
}

Objective-C

- (void)viewWillLayoutSubviews {
  [super viewWillLayoutSubviews];
  CGSize size = [_bottomNavigationBar sizeThatFits:self.view.bounds.size];
  CGRect bottomNavBarFrame = CGRectMake(0,
                                        CGRectGetHeight(self.view.bounds) - size.height,
                                        size.width,
                                        size.height);
  _bottomNavigationBar.frame = bottomNavBarFrame;
}

Bottom navigation bar

Bottom navigation bar example

API and source code:

• MDCBottomNavigationBar
  • Class source

To achieve something like the example image above, add the following code to your view controller:

Swift

bottomNavBar = MDCBottomNavigationBar()
view.addSubview(bottomNavBar)
bottomNavBar.titleVisibility = MDCBottomNavigationBarTitleVisibilitySelected
bottomNavBar.alignment = MDCBottomNavigationBarAlignmentJustifiedAdjacentTitles

let homeItem = UITabBarItem(
    title: "Home",
    image: UIImage(named: "ic_home"),
    tag: 0)
let messagesItem = UITabBarItem(
    title: "Messages",
    image: UIImage(named: "ic_email"),
    tag: 0)
messagesItem.badgeValue = "8"
let favoritesItem = UITabBarItem(
    title: "Favorites",
    image: UIImage(named: "ic_favorite"),
    tag: 0)
favoritesItem.badgeValue = ""
let readerItem = UITabBarItem(
    title: "Reader",
    image: UIImage(named: "ic_reader"),
    tag: 0)
readerItem.badgeValue = "88"

let birthdayItem = UITabBarItem(
    title: "ic_birthday",
    image: UIImage(named: "ic_cake"),
    tag: 0)
birthdayItem.badgeValue = "888+"
bottomNavBar.items = [homeItem, messagesItem, favoritesItem, readerItem, birthdayItem]
bottomNavBar.selectedItem = messagesItem

Objective-C

self.bottomNavBar = [[MDCBottomNavigationBar alloc] init];
[self.view addSubview:self.bottomNavBar];
self.bottomNavBar.titleVisibility = MDCBottomNavigationBarTitleVisibilitySelected;
self.bottomNavBar.alignment = MDCBottomNavigationBarAlignmentJustifiedAdjacentTitles;

UITabBarItem *homeItem = [[UITabBarItem alloc] initWithTitle:@"Home"
                                                          image:[UIImage imageNamed:@"ic_home"]
                                                            tag:0];
UITabBarItem *messagesItem = [[UITabBarItem alloc] initWithTitle:@"Messages"
                                                          image:[UIImage imageNamed:@"ic_email"]
                                                            tag:0];
messagesItem.badgeValue = @"8";
UITabBarItem *favoritesItem =
    [[UITabBarItem alloc] initWithTitle:@"Favorites"
                                  image:[UIImage imageNamed:@"ic_favorite"]
                                    tag:0];
favoritesItem.badgeValue = @"";
UITabBarItem *readerItem = [[UITabBarItem alloc] initWithTitle:@"Reader"
                                                         image:[UIImage imageNamed:@"ic_reader"]
                                                           tag:0];
readerItem.badgeValue = @"88";
UITabBarItem *birthdayItem = [[UITabBarItem alloc] initWithTitle:@"ic_birthday"
                                                          image:[UIImage imageNamed:@"ic_cake"]
                                                            tag:0];
birthdayItem.badgeValue = @"888+";
self.bottomNavBar.items = @[ homeItem, messagesItem, favoritesItem, readerItem, birthdayItem ];
self.bottomNavBar.selectedItem = messagesItem;

Anatomy and key properties

The following is an anatomy diagram for the bottom navigation bar:

1. Container
2. Inactive icon
3. Inactive text label
4. Active icon
5. Active text label

Container attributes

	Attribute	Related methods	Default value
Color	barTintColor	-setBarTintColor: -barTintColor	Surface color
Elevation	elevation	-setElevation: -elevation	8

Navigation item attributes

	Attribute	Related methods	Default value
Title	N/A	-[UITabBarItem initWithTitle:image:tag:] -[UITabBarItem initWithTitle:image:selectedImage:]	N/A
Unselected color	unselectedItemTintColor	-setUnselectedItemTintColor: -unselectedItemTintColor	[UIColor grayColor]
Selected color	selectedItemTintColor	-setSelectedItemTintColor: -selectedItemTintColor	[UIColor blackColor]

Icon attributes

	Attribute	Related methods	Default value
Image	N/A	-[UITabBarItem initWithTitle:image:tag:] -[UITabBarItem initWithTitle:image:selectedImage:]	N/A
Selected image	selectedImage	-[UITabBarItem setSelectedImage:] -[UITabBarItem selectedImage]	nil
Badge value	badgeValue	-[UITabBarItem setBadgeValue:] -[UITabBarItem badgeValue]	nil
Badge color	badgeColor	-[UITabBarItem setBadgeColor:] -[UITabBarItem badgeColor]	nil

Text label attributes

	Attribute	Related methods	Default value
Typography	itemTitleFont	-setItemTitleFont: -itemTitleFont	Headline 6
Color	selectedItemTitleColor	-setSelectedItemTitleColor -selectedItemTitleColor	[UIColor blackColor]

Theming

The example above is a bottom navigation bar with Shrine theming. To get started with your own theming, first add the BottomNavigation+Theming subspec to your Podfile:

pod 'MaterialComponents/BottomNavigation+Theming'

Then run the installer:

pod install

Then, import the relevant file or target and call the appropriate theming method.

Swift

// Import the BottomNavigation Theming Extensions module
import MaterialComponents.MaterialBottomNavigation_Theming

...

// Apply your app's Container Scheme to the App Bar controller
let containerScheme = MDCContainerScheme()

// Either Primary Theme
bottomNavigation.applyPrimaryTheme(withScheme: containerScheme)

// Or Surface Theme
bottomNavigation.applySurfaceTheme(withScheme: containerScheme)

Objective-C

// Import the BottomNavigation Theming Extensions header
#import "MaterialBottomNavigation+Theming.h"

...

// Apply your app's Container Scheme to the App Bar controller
MDCContainerScheme *containerScheme = [[MDCContainerScheme alloc] init];

// Either Primary Theme
[self.bottomNavigation applyPrimaryThemeWithScheme:containerScheme];

// Or Surface Theme
[self.bottomNavigation applySurfaceThemeWithScheme:containerScheme];